I had one of these growing up! It's hard to price b/c it doesn't come up very much, so it's fairly rare, but the number of people who would want it is probably somewhat limited. The damage doesn't help. If I was going to list it on eBay I might do $15-18 and see how it goes but that's not based on seeing it successfully sell.

"The U.S. Consumer Product Safety Commission has recalled several models of Magnetix toys due to a risk of magnets coming loose and injuries to children. In light of these recalls and number of products affected, unfortunately eBay has chosen to not allow any Magnetix products to be sold on eBay."

I just removed any mention of the brand from the title and brand drop-down, (and added a small parts warning,) but this may explain why it's hard to find finished listings and prices on it.